Treatment of lubricating oils



Nov. 8, 1949 P. H. CARNELL TREATMENT OF LUBRICATING OILS Filed May 24, `1946 l:o mm3 HOLVNOILOVH WnnDVA NO LVNOLLOVELI HOlVUVdBS INVENTOR.

P. H. CARNELL aNaHfLHdvN ATTORNEYS Patented Nov. 8, 1949 UNITED STATES ATENT oFF-ICE 2,487,306 TREATMENT OF LUBRICATING OILS Paul H. Carnell, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation f Delaware 12 Claims.

This invention relates to the treatment of lubricating oils to improve their properties. In one of its aspects it relates to the treatment of natural and/or synthetic polymerized olen-type lubricating oils to eiTect an improvement in their properties. In another aspect it relates to the treatment of such oils to increase their viscosity or viscosity index or stability, or a plurality of said properties. 1

The prior art on the rening of lubricating oils with anhydrous liquid hydrouoric acid shows (Frey U. S. Patent 2,378,762) .that parafiinic,

mixed-base or asphalt-base lubricating oil stock -other object Ais to provide a method of improving synthetic lubricating oils produced by polymerizing olens. Another object is to provide a method of increasing the viscosity index of lubricating oils. Another object is to provide a method of increasing the viscosity of lubricating oils. Another object is to provide a method of increasing thevstability of lubricating oils. Another object is to increase the viscosity, viscosity index and stability of mixed-base lubricating oils. Another object is to improve the properties of lubricating oils, particularly the mixed-base lubricating oils, with a minimum of loss of oil in the form of acid-solublematerial. Another object is to provide a process of the foregoing type which is simple and economical to carry out. Another object is to provide a process of the foregoing type which involves low consumption of chemicals and a maximumA recovery of lubricating oil. Numerous other objects will more fully hereinafter appear.

The accompanying drawing portrays diagrammatically one arrangement of equipment which may be used for carrying out the present invention.

Broadly speaking, my invention is a process of improving lubricating oil which comprises contacting the lubricating oil with substantially `anhydrous liquid hydroiiuoric acid and with a naphthene at elevated 'temperature and pressure for a period of time suiiicient to produce a substantial improvement in the properties of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

While any naphthene may be employed, I almost invariably use those naphthenes which are saturated cyclic hydrocarbons containing at least one saturated 5- or -carbon atom-membered ring. While the polycyclic naphthenes may be used, I prefer the monocyclic naphtheneswhich are derivatives of cyclopentane and cyclohexane. Examples of monocyclic naphthenes which ymay be satisfactorily employed are cyclopentane,

methylcyclopentane, vcyclohexane and methylcyclohexane. An example of a bicyclic naphthene is decalin (decahydronaphthalene) which embodies two iused or condensed cyclohexane rings. Other examples of bicyclic naphthenes are dicyclopentyl and dicyclohexyl. While polycyclic naphthenes having more than two saturated rings may be employed, monocyclics are more freqdently used in commercial practice.-

The exact nature of the chemical changes that occur in the treatment of the present invention is not known at the present time, but it is believed that alkylation is the principal reaction.

The lubricating oil treated in accordance with the present invention may be any hydrocarbon lubricating oil. Generally, it will be a natural 1ubricating oil, that is a lubricating oil derived from naturally occurring crude oils in known manner. The lubricating oil may be either a. paralin-base oil, a mixed-base oil or an asphaltbase oil. Generally speaking, I prefer to treat mixed-base oils in accordance with my invention since mixed-base lubricating oils may be deficient in certain respects as compared with paraffin-y base oils, although mixed-base oils possess certain advantages not possessed by vparamn-base oils. While my invention is generally applied to natural lubricating oil, it may also be applied to synthetic hydrocarbon lubricating oil especially the synthetic oil produced by polymerizing lowboiling aliphatic olens.

The oil treated in accordance with the present invention displays improved properties over the original untreated oil. One property that is improved is the viscosity index. Oil treated in accordance with the present invention has a substantially higher viscosity index than the original oil. The absolute viscosity of the oil may be increased by the treatment of the present invention, may be substantially unaected, or may be slightly lowered. In general, the stability of the oil is increased by treatment in accordance with my invention. The pour point may be increased slightly or may be the same as that of the untreated oil. Generally speaking, the gravity of the oil product of my invention is slightly above that of the initial oil. The color may be somewhat darkened by the treatment, but it is preferred that the treatment be so conducted that this darkening is not appreciable.

From this disclosure those skilled in the art will be able to conduct the treatment of the present invention in such manner as to secure the desired improvement in the properties of the oil. Reference is made particularly to the examples given below wherein diierent conditions of treatment and different naphthenes were employed with varying results.

The elevated temperature at which the treatment of this invention is carried out may vary within quite wide limits. Generally speaking, it will fall within the range of from 40 to 300 C. More commonly, it will be within the range of from 100 to 200 C. A temperature of from 140 to 170 C. is preferred and is used in the examples.

The pressure likewise may vary widely, but should be sulicient to hold the hydrofluoric acid and the hydrocarbons in the liquid phase throughout the reaction. Generally speaking, the pressure may range from 600 to 2000 pounds per square inch.

The Contact time, i. e., the time of residence of the reaction mixture in the reaction zone under the conditions of temperature and pressure noted above, should be suiiicient to produce a substantial improvement in the properties of the lubricating oil being treated. Generally speaking, this time will range from 15 to 150 minutes. A period of time ranging from 110 to 130 minutes is often preferred and is used in the examples.

It is preferred that the substantially anhydrous hydrofluoric acid be the major or dominating component of the reaction mixture, i. e., that it be present in greater amount than any other component. It is desirable to use such proportions that the hydroiiuoric acid is present in the greatest amount with the naphthene next in amount and the oil least in amount. Preferred proportions are those wherein the amount lof hydrouoric acid ranges from 1.6 to 2.0 times the weight of the oil and the amount of naphthene ranges from 1.3 to 1.7 times the weight of the oil. the amount of hydrofluoric acid substantially exceeding the amount of naphthene. These proportions are, however, not critical, but it is distinctly advantageous to use sufficient hydrofluoric acid to form a separate acid phase.

Generally the materials present in the reaction zone will consist of the oil, the anhydrous liquid hydrofluoric acid and the naphthene. Of course, -other materials formed as by-products and present in the recycle streams described more fully below may be present in the reaction zone. I refer in particular to low molecular weight cycloalkyl hydrocarbons which are recovered from the reaction mixture and advantageously recycled together with unreacted naphthene.

However, I do not wish to exclude the use of a diluent in the reaction zone. Such a diluent will generally be a condensible paraihn, usually a liquid paraffin such as liquid propane, liquid normal butane or normal pentane or normal hexane. As disclosed more fully below, in a modication of the present invention I may use an aliphatic paran, particularly an aliphatic isoparaiin and especially an aliphatic C4 to Cs isoparafn as a component of the reaction mixture to produce certain advantageous results noted below. Such an aliphatic paraffin may, of course, additionally serve to dilute and render less viscous the reaction mixture.

Other than by-products such as cycloalkyls which may be present in certain recycle streams as noted above, however, the reaction mixture will consist of the lubricating oil to be treated, the liquid hydroiluoric acid, and the naphthene, an aliphatic paraflin being optionally present, all other materials being excluded from the reaction system.

The amount of hydrouoric acid is almost invariably such that a separate acid phase is present in the reaction zone. Any suitable equipment for carrying out the reaction may be employed. Generally, however, the equipment will be so designed as to provide intimate contacting between the acid and the hydrocarbon phases throughout the reaction period. The contacting equipment may be similar to or identical with the contactors which are commonly used for conducting the alkylation of aliphatic'isoparailins with aliphatic olens. An example is the so-called Stratco contactor. Any other means of maintaining a ne emulsion of the acid and hydrocarbon phases may be employed. The equipment used should be provided with means for maintaining the clevated temperature' desired for the reaction. This means may take the form of indirect heating arrangements of known type.

Following agitation of the reaction mixture for the selected contact time at the elevated temperature and pressure employed, the reaction mixture may be withdrawn from the reaction zone and allowed to cool and settle, usually by gravity, into two separate layers, namely, a lower acid layer and an upper hydrocarbon layer. These layers are separated in any suitable manner. The treated lubricating oil may then be recovered from the hydrocarbon layer. For example, the hydrocarbon layer may be washed with dilute caustic solution and then topped under vacuum to the initial boiling point of the untreated lubrieating oil to remove 10W-boiling constituents.

Generally, however, it will be preferred to subject the hydrocarbon layer to vacuum fractionation to recover a light fraction containing unreacted naphthene and low molecular weight cycloalkyl hydrocarbons, produced as by-products in the reaction, from a bottoms fraction of the treated lubricating oil. This bottoms fraction may then be washed with dilute caustic solution to give the finished oil. The acid layer comprises hydrouoric acid containing in solution acid-soluble oils derived from the original oil and I have found that when particular lubricating oils, such, as those derived from mixed-base crudes, are treated' withA liquid anhydrous hydrofluoric acid and a naphthene, particularly'cyclohexane, product oils with high stability and highv viscosity indices result, but the oils are darker than the original oils and:v have an undesirably high cloudi point. I have found,y however, that this undesirable effect may be overcome by using an aliphatic paraffin in conjunction with the naphthene.

In accordance with the latter aspect of my invention, lubricating oils of high stability, high` Viscosity index, improved color and low cloud point may be obtained by treating lubricating oils, especially mixed-base lubricating oils, with a mixture consisting oi liquid. anhydrous hydroiluoric acid, an aliphatic paraffin, particularly an aliphatic isoparafn, and especially an aliphatic isoparafn having from four to six carbon atoms per molecule, and' a naphthene; particularly cyclohexane.

Any aliphatic C4 to C6 parahin may be employedv in this modification of my invention but I prefer, an isoparaflin, namely, either isobutane,I isopentane or isohexane. Isopentane is preferred.

. The conditions oi. treatment are the saine as those given above in detail for thetreatment with hydroluoric acid and a naphthene alone.

When an aliphatic parahin, such as a C4 to. Ce isoparaflin, is used, the total, amount Ofaliphatic parafiin plus naphthene may'range fromI 1.3 'to 1.7 times the Weight of the oil. Amounts beyond these limits may, however; be effectively used if desired. 'Ihe proportionl of the aliphatic para-ihn in the combined aliphatic parailin plus naphthene may range from to 60 per cent by Weight, but is preferably from 40 to 60 per cent by weight of the total amount of naphthene plus isoparain. Ordinarily, approximately equal volumes oftheI naphthene and the isoparaflin will be employed. The proportion: of-hydrofluoric acid employed may be the sameV as that given above, namely; from 1.6 to 2.0 times 'the weight of 'the oil, but other proportions may be eiectively used, provided that suiicient acid is present to form aseparate liquid phase.

Preferably this embodiment of my invention is conducted by using isopentane in conjunction with cyclohexane for the modiiication of the lubricating oil. Ordinarily, approximately equal. volumes of isopentane and cyclohexane are employed.

In another aspect ofiny invention, I use methyl-cyclopentane. as the naphthene. I have found that when certain lubricating oils, particularlythose derived from mixed-base crudes, are treated with liquid anhydrous hydrouoric acid and a naphthene other than methylcyclopentane such as cyclohexane, cyclopentane, decalin, methylcyclohexane, etc., or with hydroiluoric acid and a mixture of an aliphatic paramn and a naphthene such as a mixture offi'sopentane and; cyclohexane,

. treated oil is: converted to. acid-soluble material,

which represents a loss of material and: is a. relatively undesirable ley-product oi. the process.

I have found, however, that when methylcyclopentane is. the naphthene employedfor-the treatment, these objections are overcome. For ex;- ample, upon treatment of a. mixed-base lubricating oil with. hydroflu'oric acid: and methylcyclopentane in accordance With my inventiom the lubricating oil produced has high stability, high` viscosity index. and increasedr viscosity. Yet only a. small portion of the oil is converted to acidsolubleoil. Theconditions and proportions given above apply equally to this modification of my invention.

Although. the chemical changes that takeplace.

when a mixed-base lubricating oil s treatedl with:- anhydrous. liquid hydroiiuoric acid andj methyl-` cyclopentane is alkylatedmore easily by certainfr constituents of the oil. In treating oil with liquid anhydrous hydrouoric acid and methylcyclo pentane, the same conditions and` proportions; oi".`

reactants whichy are given inl detail above are. employed.

In particular instances, it may be advantageous to treat the lubricating oils with a mixture., ci naphthenes, such: as cyclohexane' and methylcyclopentane, whereby oils of high viscosity index and stability are obtained with a minimum off oil being converted to acid-soluble oil. Mixtures of two or more-naphthenes and an aliphatic parahin may also be used.

Pis-mentionedy above, thel process of my invention is applicable not only to natural lubricants but also tosynthetic lubricating oils produced by polymerizing oleiins. such synthetic lubricating oils is thatF theiry 'viscosity-Y index is-comparatively low. Treatment of such oieiinv polymers with liquid anhydrous hydroiiuoric acid and a naphthene, such as cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane, yields a lubricant having' increased' viscosity index and degree of saturation.

One example of a synthetic oil is the type produced' by pol'ymerizing low-boiling aliphatic ole- :tinsv ci atleast threecarbon atoms per molecule with a zirconium tetrahalide catalyst under controlled conditions as taughty in U. S. Patent to Reid, No. 253893240.

The conditions for treatment of olen polymer in accordance with this invention are, in general, the same as"` those previously described` for treatment of natural lubricating oils and the considerations advanced above apply. The same ranges of relative proportions are empioyed. The optimum conditions in any given instance depend on the nature of the specihc polymer treated and. the specific naphthene used, and can readily be determined by trial. In many. cases the temperature of' treatment will cover a lower range, say from 40to 200 C'. instead of 40 to 300 C. asgiven. for' the natural oils. y

One disadvantage of some Following 'are specific examples of the treat- Table A ment of lubricating oils with hydrofluoric acid in the presence of a naphthene or a mixture of Bollmg Vol- Weight Reime' Viscosfy Fraction Range urne Per Cent ve Index naphthene and ahphatie paraffin. The procedure NSF.. m1] o(omge, rgef. (Druxi and employed in Examples 1 to 6 was as follows. 5 mm m5) A 4 5-liter steel bomb was charged with liquid UN'IREATED OIL anhydrous hydrouorio acid, a mixed-base lubri- B 3o 1 4872 35 eating oil, a cycloparailln, and, when desired, an 13.27 1.4842 75.0 aliphatic parain. The charged bomb was 825 clamped to arocker and was fitted with a suitable 13.45 114860 "f pressure gauge. The bomb was heated and agi- 13'06 1-4870 59-0 tated for the desired time and was removed from 13.33 1.4994 33.5 the rocker and placed in a vertical position. The -17 contents of the bomb were allowed to cool and HF.CycL0HEXANE-TREATED OIL settle. The acid and hydrocarbon layers were 15 separated, and the hydrocarbon layer was washed li/,Ilmi 537'657 28 8'47 65'7 with dilute caustic solution. The acid layer was 1 657-772 105 gheated to remove hydrofiuoric acid, and the resi- 7180 4821 9810 due was weighed. The hydrocarbon layer was then topped to 450 F. at approximately 2 to 3 414 114882 9020 mm. pressure (the initial boiling point of the unggg 1-4956 85-0 treated oil) to remove low-boiling constituents.

The following data were obtained: 1 Cracking occurred- EXAMPLES 1 TO 6 Example Untreated 011 990 953. Aliphatic para Isopentane.. Alipliatic parain, gms 3 Cycloparain Methylcy- Cyclohexane Cyclohexane Methylcycloclohexane. pentane Cycloparain, grams Contact time, miuutes Maximum temperature, C- Maximum pressure, p. s. i... Weight percent acid-solubles..

Test Data Inspection of the data obtained shows that when a mixed-base lubricating oil is treated with hydrouoric acid and a naphthene, an oil with a substantially increased viscosity index is obtained. From Example 4, it -appears that decalin gives the least improvement in viscosity index. Comparison of the data given for Example 6 with the other examples shows that when methylcyclopentane is used, both the viscosity and the viscosity index are substantially increased and yet a minimum amount of acid-solubles is produced. The data for the other examples indicate that this effect is not shown by the other naphthenes studied or by a mixture of an aliphatic paraffin and a cycloparain (Example 3).

Comparison of the data obtained in Example 3 with those obtained in Example 2 shows that the product oil from Example 3 has a considerably lower cloud point, a lower pour point and a lower ASTM color than the oil from Example 2. The data for Example 1 show that treatment of a mixed-base lubricating oil with hydrofluoric acid and methylcyclohexane does not raise the cloud point materially. The viscosity index for the product oil from Example 3 is greater than that for the oil from Example 1.

Samples of the untreated oil and the product oil from Example 2 were vacuum fractionated and the viscosity index and refractive index of each fraction were determined. The data set forth in Table A were obtained.

These ldata show that treatment of the oil with HF and cyclohexane produces a considerable chemical change in the oil.

Aluminum block stability data obtained for the untreated oil and the product oils from Examples 2 (blend of fractions 1 through 6) and 6 are tabulated as follows:

These data show that the HF-cyclohexane and HF-methylcyclopentane treated oils have greater stability than the untreated oil.

ansa-see 9 EXAMPLE vl This example 'shows 'theresults vof treatment of 'an `ole'ln polymer "in accordance 'with "the present invention. This example consists of two parts, namely, Part A which includes 'the preparation of the olefin ,polymer, and LPart 'B vwhich'includes the treatment of the olefin polymer with hydroluoric ac'id and methylcycl'ohexane.

A.-Preparaion of vOleyrz. Polymer An 18-liter steel reactor provided with ia mechanical stirrer was charged 'with '450 'grams -of zirconium tetrachloride lcatalyst 'and 1 gallon of 'normal pentane. 'Thirteen and four-tenths pounds lof propylene was gradually added to the .Bf-Treatment -ofoleyin polymer in accordance with ithe intention Four hundred ninety-:eight grams of the polymer as produced in A,'11'51,grams of methylcyclo- "hexane, and 1026 grams of commercial anhydrous hydrouoric acid were-charged to a 4.5-liter steel bomb. The charged bombwas clamped to a platform rocker and was fitted with a suitable pressure gauge. The bomb was continuously heated and agitatedv for "120 minutes. The maximum temperature was 151 C.; maximum pressure, 635 pounds per square inch. The bomb was removed from the rocker and placed in a vertical position. The bomb contents were allowed to cool and settle and the lacid and hydrocarbon layers were separated. The hydrocarbon layer was washed with dilute caustic solution and 'was separated and dried. After ltering through 'a Tilter aid, the product hydrocarbon was topped at 450 F. and 5 mm. The 'following test data were obtamed:

Hydro fluoric Acid- Untreated Methyl- Polymer cyclohexane-Treated :Polymer Viscosity, 100 F., SUS 449. 6 270. 9 Viscosity, 210 F., SUS 54.11 4S. 37 Viscosity Index (Dean & Davis) 48 62 Your Point. F -30 API Gravity. 37.2 38.2 ASTM Color4 1 Refractive Index (20 1:4681 A1.4620

bln the drawing, vthe reactor l is charged with lubricating oil to be treated by vmeans of line A2, with anhydrous hydroiluoric acid via line 3, and with .naphthene hydrocarbon via Eline d. If an aliphatic paramn is .to be 'employed Ain the treatllO zarator 6 which maybe of =a type such as is known .for the separation oi the eiiiuent from the hydro- .fuoric acid ankylation 4.of Iisoparanins with aliphatic lvoleiins. In lseparator 6 the acid and hr3- drocarbon layers are separated, usually by means of gravity. 'The acid lay-er is passed via line 'l to fractionator -3 wherein it is separated into an overhead fraction of hydroiluoric acid which is recycled via 4line 9 and a bottoms fraction of acid residue which iis withdrawn vvia line l0. The acid yresidue consists of the .acidesoluble material dissolved by the acid in the reactor l.

The hydrocarbon layer from separator 16 is passed via line il to vacuum fractionation column l2. Naphthene and 10W molecular weight cycloalkyls .may cbe separated and recycled 'via line i3. If an aliphatic paraffin ywas charged-to reactor l, a stream of unreacted aliphatic paraffin `may be withdrawn yfrom vacuum fractionator ri2 and recycled via line 1M. Lubricating voil @from vacuum rfractionator l2 is withdrawn via .line l5 as a product of the process. uct voil Amay be washed -with caustic solution to remove hydroiiuoric acid.

It Iwill be understood that vacuum vcolumn i2 and the takeonc lines YI3 `and lli are shown merely diagrammatica'llv If an aliphatic paraffin was charged, it may be desirable to recover a lsingle overhead fraction containing the :unreacted aliphatic paraflin, naphthene and the low molecular weight cycloalkyl compounds and to recycle v:these without separation. However, better control .over the reaction may be Aobtainable by separately recovering and recycling the two fractions :shown in l lines -IS and I4 since such separate recycle enables more accurate metering -of reactants to lreactor l.

ment, it is charged via line 5. The reactants are l product low molecular Weight cycloalkyl roompounds, rand .'naphthene hydrocarbon, :and raliphatic `paraffin if .that was us.ed,:is1passed to :sep-

From the foregoing description, .it will be Vseen that the present invention Vprovides a simple and Veconomical process for improving lubricating oils. The :process is particularly vvaluable for the improvement of mixed-base lubricating oils `which .iin the past have been considered to have certain disadvantages relative to paran-base lubr'icat ing .oils, although 'it was recognized that mixed base oils vhad certain advantages not possessed by the paraffin-base oils.`

Speciically, the present invention enables a substantial increase vin viscosity `index and stability of the oil to be brought about. The -invention also enables olefin polymer types of synthetic lubricating oil to be improved materially.

I claim:

l. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous 'liquid hydrofluor'ic acid 'in proportion suiTicient to -form a separate acid phase and with an added naphthene selected from -a group consisting of cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane in an amount ranging from 1.3 to 1.7 times the weight of said oil at elevated temperature of from 40 to 300 C. at a pressuresufcient to maintain the hydrofluoric acid and hydrocarbons'in liquid phase for a period of time suiiicient to produce a substantial increase in the viscosity index Aand stability of said lubricating oil, and recovering the treated lubricating oil from the resulting'reaction mixture.

2. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially vanhydrous liquid hydrofluoric acid in proportion suicient to form a'separate acid Aphase and with added :methylcyclohexane .in .an amount ranging Y.from :1.3 to 1-.7 times the If desired, the prodweight of the oil at elevated temperature of from 40 to 300 C. and at a pressure sufficient to maintain the hydroluoric acid and hydrocarbons in liquid phase for a period of time suiicient to produce a substantial increase in the viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

3. The process ofV improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous liquid hydrouoric acid in proportion suicient to yform a separate acid phase and with added cyclohexane in an amount ranging from 1.3 to 1.7 times the weight of the oil at elevated temperature of from 40 to 300 C. and at a pressure suiiicient to maintain the hydrouoric acid and hydrocarbons in liquid phase for a period of time sufficient to produce a substantial increase in the Viscosity index and stability oi said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

4. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous liquid hydrouoric acid in proportion suil'cient to form a separate acid phase and With added methylcyclopentane in an amount ranging from 1.3 to 1.7 times the Weight of the oil at elevated temperature of from 40 to 300 C. and at a pressure suiicient to maintain the hydrofluoric acid and hydrocarbons in liquid phase for a period of time suicient to produce a substantial increase in the Viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

5. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous liquid hydrofluoric acid in proportion suiicient to form a separate i;

acid phase and with added naphthene selected from a group consisting of cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane in an amount greater than said lubricating oil While maintainingra temperature of from 40 to 300 C. and a pressure sufcient to maintain the hydrofluoric acid and the hydrocarbons in liquid phase for a period of time ranging from to 150 minutes and suicient to produce a substantial increase in the viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture. f

6. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous liquid hydro-fluoric acid in proportion sucient to form a separate acid phase and with added naphthene selected from a group consisting of cyclopentane, methylcyclopentane, cyclohexane, and methylcycohexane in an amount greater than said lubricating oil While maintaining a temperature of from 140 to 170 C. and a pressure sufficient to maintain the hydrofluoric -acid and the hydrocarbons in liquid phase for a period of time ranging from 110 to 130 minutes and sucient to produce a substantial increase in the Viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

7. The process of improving lubricating oil which comprises subjecting a mixture consisting of said lubricating oil, substantially anhydrous liquid hydrouoric acid and an added naphthene selected from a group consisting of cyclopentane,

methylcyclopentane, cyclohexane, and methylcyclohexane, the proportions in said mixture being such that the hydrofluoric acid is greatest in amount, the naphthene is next in amount and the oil is least in amount, to an elevated temperature of from 40 to 300 C. and a pressure sufficient to maintain the hydrofluoric acid and the hydrocarbons in liquid phase for a period of time ranging from 15 to 150 minutes and sufficient to produce a substantial increase in the viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

8. The process of improving lubricating oil which comprises subjecting a'mixture consisting of said lubricating oil, substantially anhydrous liquid hydroiluoric acid and an added naphthene selected from a group consisting of cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane, the proportions in said mixture being such that the amount of hydrofluoric acid ranges from 1.6 to 2.0 times the weight of said oil and the amount of naphthene ranges from 1.3 to 1.7' times the weight of said oil, to a temperature of from 140 to 170 C. and a pressure sumcient to maintain the hydrofluoric acid and the hydrocarbons in liquid phase for a period of time ranging from 110 to 130 minutes and sufcient to produce a substantial increase in the Viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

9. The process of improving mixed-base lubricating oil which comprises contacting said mixed-base lubricating oil with substantially anhydrous liquid hydrouoric acid in proportion suiicient to form a separate acid phase and with added methylcyclopentane in an amount greater than said lubricating oil While maintaining a temperature of from to 200 C. and a pressure suicient to maintain the hydrouoric acid and the hydrocarbons in liquid phase for a period of time ranging from 15 to 150 minutes and sufficient to produce a substantial increase in the viscosity index, viscosity and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

l0. The process of improving lubricating oil which comprises contacting said lubricating oil with substantially anhydrous liquid hydrouoric acid in proportion suiicient to form a separate acid phase and with an added C4 to Cs aliphatic parafiin and an added naphthene selected from a group consisting of cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane in an amount such that the total amount of aliphatic paranin plus naphthene ranges from 1.3 to 1.7 times the weight of said lubricating oil and the amount of said aliphatic paraffin ranges up to 60 per cent by weight of the amount of added aliphatic paraffin plus added naphthene at elevated temperature of from 40 to 300 C. and at a pressure suiiicient to maintain the hydrofluoric acid and hydrocarbons in liquid phase for a period of time sufficient to produce a substantial increase in the viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixure.

1l. The process of improving mixed-base 1ubricating oil which comprises contacting said mixed-base lubricating oil with substantially anhydrous liquid hydroiiuoric acid in proportion sumcient to form a separate acid phase and with added isopentane and added cyclohexane in an ane ranges from 1.3 to 1.7 times the Weight of said lubricating oil and the amount of said added isopentane ranges from 40 to 60 per cent by Weight ofthe amount of added isopentane p us added naphthene at elevated temperature ci' from 40 to 300 C. and pressure suflicient to maintain the hydrofluoric acid and hydrocarbons in liquid phase for a period of time suicient to produce a substantial increase in the viscosity index and stability of said lubricating oil, and recovering the treated lubricating oil from the resulting reaction mixture.

12. The process of improving synthetic lubricating oil produced by polymerizing olens which the weight of said oil while maintaining a temperature of from li0 to 200 C. and a pressure suf'- cient to maintain the hydrouoric acid land. the hydrocarbons in liquid phase for a period of ltime ranging from 15 to 150 minutes and suflcient to produce a substantial increase in the viscosity The following references are of recordv in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,320,629 Matuszak June 1, 1943 I 2,366,743 Matuszak Jan. 9, 1945 2,375,675 Matuszak May 8, 1945 2,378 762 5 Frey June 19, 1945y 

